1. Field of the Invention
The present invention relates to a semiconductor device including an oxide semiconductor and a manufacturing method thereof.
2. Description of the Related Art
Various metal oxides are used for a variety of applications. Indium oxide is a well-known material and is used as a transparent electrode material which is necessary for liquid crystal displays and the like.
Some metal oxides exhibit semiconductor characteristics. For example, metal oxides exhibiting semiconductor characteristics include tungsten oxide, tin oxide, indium oxide, zinc oxide, and the like, and thin film transistors in which a channel formation region is formed using such a metal oxide exhibiting semiconductor characteristics have already been known (see Patent Documents 1 to 4 and Non-Patent Document 1).
Further, not only single-component oxides but also multi-component oxides are known as metal oxides. For example, InGaO3(ZnO)m (m: natural number) belonging to homologous series has been known as a multi-component oxide semiconductor including In, Ga, and Zn (see Non-Patent Documents 2 to 4).
Further, it is proved that an oxide semiconductor formed using an In—Ga—Zn based oxide as described above can be used for a channel layer of a thin film transistor (see Patent Document 5 and Non-Patent Documents 5 and 6).